Copolymers of acrylic and vinyl monomers in organic solvents are distinguished by a number of outstanding properties, including for example resistance to hydrolysis and stability in storage, minimal yellowing, high weather resistance and good gloss retention. The solvents used can seriously affect the economy of the binder systems produced from the binders, because the solvents are not incorporated in the coatings during the stoving process, but instead have to be additionally eliminated, for example by subsequent burning, to reduce environmental pollution as far as possible.
It is known (cf. for example G. Y. Talak, S. P. Pontis, Paint & Resin 12/83, pages 34 et seq., DE-OS No. 3 209 421, EP-A No. 95 263 or EP-A No. 105 293) that it is possible to use copolymer-based water-dilutable binders which generally contain emulsifiers to stabilize the aqueous binders or relatively large amounts of organic auxiliary solvents. The emulsifiers can adversely affect the lacquer properties of the coatings, for example resistance to water and detergents, weather resistance and/or gloss.
The use of relatively large quantities of organic solvents in water-dilutable binders generally originates from the production process because it provides for a stirrable viscosity and for controlled heat exchange during the polymerization or polycondensation reaction and the lacquers thus produced show a more favorable property level of the corresponding coatings in regard to levelling, crater formation and gloss.
EP-A No. 0 218 906 describes water-dilutable copolymers which do not contain any emulsifiers and which may be processed in combination with crosslinker resins to form lacquers containing less than 5% organic solvents. The lacquers and the films obtained from them are distinguished by a balanced overall property level.
For various applications, such as for example clearcoat binders, it is desirable to improve both the elasticity values and also safety of application for relatively high layer thicknesses under adverse conditions, including for example short airing times, high air humidity, low temperatures.